Two-stroke internal-combustion engine



March 11, 1930. w. ULRICH 1,749,859

TWO-STROKE INTERNAL COMBUSTION ENGINE Filed Jan. 11, 1928 INVENJITORF Wilhelm ULRICH @ZKQLIEAYZ Patented Mar. 11, i930 UN ED-S A S PATENT, OFFICE wILnELm: omen, or xmn; emmY, AssIexon. sro nnu'rscnn wnaxn xInL Ax- -'IIENGESELLSGHAIT, or. KIEL, GERMANY, A CORPORATION or GERMANY TWO-STROKE MERE-COMBUSTION ENGINE Application fll6d I3n118Iy 11, 1928, semi ll'o.

The invention concerns the scavenging of two-stroke internal combustion engines with inlet and exhaust ports controlled by the piston. Before giving the characteristics of the invention, the mam' kinds of known scavenging processes will be explained.-

With cross scavenging the inlet ports are arranged only on one side of the cylinder 10 and the outlet ports on the opposite side in substantially the same plane. The scavenging air is introduced into the cylinder in such manner that it rises up the wall of the cylinder above the inlet ort. It is deflected by the cover and then ows down over the opposite side of the cylinder to the outlet port. 1 j v p The lateral reversing scavenging is charac terized by the fact that the inlet and outlet ports are arranged in two planes one above' the other. The scavengin air is 'ded the cylinder wall opposite to the gldt poi' t sl and not perforated y outlet ports and after deflection at the cylinder cover flows down zs'over the opposite wall to the outlet ports disx osed above the inlet ports.

g ith central reversing "scavenging the scavenging air enters through ports arran d around the whole periphery of the cylin er,

o rises up in the longitudinal axis of the cylinder, is deflected at the cylinder cover and flows around the cylinder wall to outlet ports similarly arranged overthe whole circum' firencelpf the cylinder'above the inlet ports T e central reversing scavenging has the advantage over cross scavenging and lateral reversing scavenging, that the inlet and outlet ports can be arranged around the whole circumference of the cylinder so that for admission and exhaust a greater total cm sectinnal area is available with relatively little lost stroke. With theother scavenging processes on the other hand the cylinder wall above the inlet ports is required for guiding the scaven 'ng air and may therefore not be interrupted: at least not over the whole pe riphery, b 'outlet ports. Consequently -w th the centra "reversing scavengin for the same" quantity of air a lesser height 0 port is neces- 846,051, and in Germany December 19, 1924.

sary than with these other scavenging processes and there is therefore a reduction in lost piston stroke and overall height of the engine, 'or with a similar height of port a lower pressure of scavenging airvand a. saving in work of compression and therewith an improved efiiciency of the engine is attained.

The other scavenging processes have moretherefore have the preference over the other scavenging processes if it did not have the disadvantage that the scavenging stream rising in the cylinder, as practice has shown, is not stable, but oscillates to and fro whereby eddies are set up which unfavorably effect the scavenging.

The present invention solves the problem of obviating this disadvantage of central reversing scavenging, in that the streams of air entering the cylinder'are influenced by the irregularity in the introduction of the air in such manner that the combined cur-,

rent of air rises at an inclination to the c l- ,inder axis and retains this direction. e

rising air stream is thus stabilized so that the striking action of the scavenging stream and the formation of eddies is avoided. v

The irregular form of the means serving, to introduce the air is so designed that on .the one hand the streamlets contacton opposite sides so that premature escape of the scavenging air through the outlet ports is prevented, and on theother hand however it is assured that the combined stream rises in the cylinder in a definite constant inclined 'me nt of ports in the .central reversing scavenging are combined with those of a stable flow of the stream.

.The accompanying drawings illustrate at Fig. 1 a longitudinal section of a cylinder constructed according to the invention;'Fig.

2 a cross' section along the line ss of Fig. 1

.and Fig. 3 a longitudinal section with a modified form of piston.

a indicates the cylinder, 6 the piston situated at the lower dead centre. The ports ing said intake ports, said channel being disposed unsymmetrically of the cylinder axis, a bafiie on said piston, said baflle being disposed unsymmetrically of the cylinder axis, by which unsymmetrical disposition of said air supply channel and of said piston baflle said scavenging air rises in the cylinder obliquely to the axis of the latter.

.. WILHELM ULRICH.

0 for the admission of scavening air and the cylinder is so graduated that a continualexcess pressure of the streamlets entering on one side of the cylinder over those entering the opposite side is produced. The combined der is thereby diverted from the longitudinal axis of the cylinder and towards the weaker portionsof the stream. The rising stream is inclined to the cylinder axis towards the cover and constantly retains this direction. J

stream of scavenging air rising in the cylin- It is deflected at the cover and then again disperses into streamlets which flow down on .ture exhaust of the stronger streamlets all sides to the exhaust ports. The premathrough the exhaust ports is prevented by theweaker streamlets. Contrary to the lateral reversing scavenging no closed cylinder 40 wall is necessary-here for guiding the rising scavenging stream; the latter guides itself. I

The stabilizing of the flow of thestream can be assisted by the unsymmetrical form 45 Figure 3 of the drawings.

' The invention is suitable for constant-pressure as well as for constant volume combustion engines.

I cla 1m: 1. In a two stroke internal combustion engine, a cylinder, apiston in said cylinder, a

plurality of annular scavenging air ports in said cylinder, a lurality of annular'exhaust ports in said 0 inder in a plane above said intake ports, a afile on said piston, said baffie b'eing disposed'unsymmetrically of the cylinder axis, by whichs'aidscavengingair rises in the cylinder obliquely to the axis of the latter. 4

2. In a two stroke internal combustion engine, a cylinder, a piston in said cylinder, a

. pluralit of annular scaven said cyhnder, a plurality o annular exhaust intake port's, an air supply channel surround- I of the top of the piston as illustrated in g air ports in Q us I ports in said cylinder in a plane above said 

